This invention relates to a rail engagement apparatus for a road vehicle. More specifically, this invention relates to a rail engagement apparatus mountable upon a road vehicle and having railway wheels which may engage the rails even when the vehicle is not centered over the track.
Railroad service crews often have to go to various places along a railroad track in order to make repairs and inspections. Depending upon the type of service which is to be performed and other factors, the service crew may ride to the work site using a rail vehicle or using a road vehicle, such as a truck or car. Since the best way to a work site may include travel along a road and travel along a railway, service crews and other rail workers often have used road vehicles having a rail engagement or guide wheel apparatus mounted on them. Such cars or trucks may travel along a highway or other road with road wheels engaging the road. Upon getting to an appropriate place along the railway, the rail engagement apparatus is operated such that railway wheels are lowered from the vehicle until the vehicle is bound to the railway. Usually such vehicles include an apparatus at the front of the vehicle which lifts the front road wheels off the ground when two front railway wheels engage rails and an apparatus at the back of the vehicle, which apparatus secures the back of the vehicle to the rails by two back railway wheels. The two back railway wheels usually allow the regular road wheels to contact the rails or other surface such that the road wheels may provide traction to move the vehicle even when the two front railway wheels and two back railway wheels have secured the vehicle to the rail. When the vehicle wishes to leave the railway, the two front railway wheels and the two rear railway wheels are retracted or lifted up such that the vehicle may again run along the road.
Various structures have been used to allow railway wheels to be attached to road vehicles. Although such structures have been generally useful at moving the railway wheels between an upper position in which the vehicle may travel along a highway or other road and a lower position in which the vehicle travels along a railway, such structures have often been subject to one or more of several disadvantages.
When the driver of a vehicle wants to lower the rail wheels for engagement with the rails, the driver must stop the vehicle such that it is centered over the rails. It is often difficult to get the rear of the vehicle centered over the rails. The driver may have to try more than once in order to get the rear of the vehicle centered over the rails such that lowering of part of the apparatus will cause the rear rail wheels to engage the rails.
A further problem some railway guide wheel devices designed for the rear of a vehicle is that they may not include any type of suspension. Since at least some of the rear wheels of the vehicle are supporting a portion of the vehicle weight, such designs do not include any provision for dampening vibration from the railway wheels. In addition to decreasing the comfort of anyone in the vehicle, such arrangements without a suspension for the rear railway wheels occasionally result in the rear railway wheels disengaging from the rails.
A further problem with many railway guide wheel devices is that they often have very limited ground clearance. In other words, when such devices are disposed in a road mode with the railway wheels in an upper position, the railway wheels and other parts of the mechanism may remain closer to the ground than is desirable. Since such vehicles may often have to be driven upon dirt roads or other irregular surfaces, such limited ground clearance is a significant disadvantage in many such designs.
U.S. Pat. No. 4,583,465 issued Apr. 22, 1986 to Powell shows a railway guide wheel apparatus for the rear of a vehicle. That apparatus does have the ability to side shift a wheel support axle such that the vehicle does not need to be precisely aligned with the railway tracts in order for the railway wheels to engage the rails. Two pairs of toggle structures are used in combination with two hydraulic cylinders in order to provide for the side shifting of the wheel axle. However, the same hydraulic cylinders which are used to provide the side shift are also used to lower the wheels such that shifting the wheel support axle sideways may require one to lower one end of the axle below the other end of the axle. In addition to requiring careful coordination of the control of both hydraulic cylinders in order to get the rail wheels into engagement with the rails, centering of the vehicle relative to the wheel support axle requires further activation of the two hydraulic cylinders.